This application claims the priority of German patent document 101 50 276.1, filed 12 Oct. 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for determining the temperature of a wheel-braking device in a brake system, particularly an electrohydraulic, electropneumatic or an electromechanical brake system.
In brake systems of this type, at least in the normal operating state, there is no mechanical or hydraulic connection between the brake-operating element and the wheel-braking devices. Moreover, braking action may be restricted due to an increased operating temperature in the region of the brake discs or, where an electrohydraulic brake system is concerned, in the hydraulic fluid. In vehicle brake systems with a fluidic or mechanical connection between the brake-operating element (for example, the brake pedal) and the wheel-braking devices, the driver receives feedback on the decrease in the braking action by observing a change in the actuation necessary to produce the same braking action (for example, the brake-pedal travel becomes longer). However, such feedback is no longer available in recent brake systems, since the brake-operating element is uncoupled mechanically or fluidically from the wheel-braking devices of the vehicle.
It is known from German patent document DE 42 35 364 A1 to determine the current disc temperature from the heat supplied to the brake disc during braking and, if there is no braking operation, from the heat discharged from the brake disc. When the disc temperature exceeds a limit value, a warning to the driver is generated.
One object of the present invention is to provide an improved method for determining the temperature of the wheel-braking device.
This and other objects and advantages are achieved by the method according to the invention, in which the current disc temperature of the brake disc is determined based on the last-determined disc temperature, the energy supplied to the brake disc since the last temperature determination, and the energy discharged by the brake disc since the last temperature determination. The current caliper temperature of the brake caliper of the wheel-braking device is determined by means of the current disc temperature of the brake disc.
Particularly with regard to hydraulically actuated brake jaws, the caliper temperature is, as a rule, more critical than the disc temperature, since the brake caliper heats the fluid actuating the brake jaws to a substantially greater extent than the brake disc and a decreasing braking action can consequently occur.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.